Bond angles distortion

In reality, several factors were mentioned as being responsible for this behavior, such as variations in bond angle distortion, in the internal stress or in the hydrogen content [40, 76], but all of them are also strongly correlated with the variation of optical gap width in amorphous carbon films. Theoretical work on Raman spectroscopy on DLC materials gave additional support for Dillon s interpretation [77]. 

Fig. 2.6 Comparison of the calculated structures for glycine in the gas-phase and in water (COSMO solvation model). Note that the central bond angle in the zwitterionic form 1 is distorted by the hydrogen bond length of 1.96A computed for this structure in the gas phase. When solvation effects are included in the calculation using COSMO, the electrostatic interaction is reduced in magnitude due to charge screening by water, and the bond angle distortion is no longer present.

The strain estimates in these systems have been made on the basis of bond-length and bond-angle distortions (89), and it would be interest-... 

Comparison of the heats of combustion of cycloalkanes (Table 9.1) shows that cyclopropane, cyclobutane, and cyclononane yield more energy per methylene group than the other cycloalkanes. This can be attributed to strain resulting from bond-angle distortion (Baeyer strain), eclipsed conformations (Pitzer strain), and trans-annular, repulsive van der Waals interactions. Common (five- and six-membered) rings and large (more than twelve-membered) rings have little or no strain. This... 

Isotope effects are vibrational in origin206-210. It has been claimed213 that the isotope shift must involve the in-plane C—N—H bending vibrations and the associated C—C—XH bond-angle distortions. This distortion can be regarded as a perturbation on the hybridization which, in conjugated systems, is likely to spread over the whole... 

Fig. 19.3. Ramachandran plots illustrating the sterically allowed regions for d>, y/ for glycine (left) and for the other 19 amino acids (right). The fully allowed regions are indicated by shading, the partially allowed regions by thick lines, the connecting region enclosed by the dashed lines is permissible with slight bond angle distortion. Secondary-structure conformations are aR, a-helix 3, 3,0 helix aL, left-handed a-helix 0 antiparallel and parallel yff-sheet [586]...

Fig. 3.1. Calculation of the dependence of Si—Si bond energy on (a) bond length and (h) bond angle. The average bond angle distortions in a-Si H are shown (Biswas and Hamann 1987).

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